Several prior art methods of depositing and protecting dielectric-metal coatings are known such as the method described in U.S. Pat. No. 7,648,808 issued to Buchsbaum et al., which deals with a final blanket coat deposited on top of patterned features. In the Buchsbaum disclosed method features are patterned and deposited using a lift-off process followed by a novel final blanket coating step that completes the coating stack and results in passivation of the metal layer edges. The passivation of the metal layer edges prevents oxidation and corrosion of the metal. The final blanket layer can be a group of layers such as a final cavity mirror, anti-reflection layers, or a single layer of a material. These layers may use materials specifically selected for their corrosion resistant properties. This prior art technique is compatible with partially or fully populated patterned areas but utilizes a continuous blanket coating over the coated and uncoated patterned regions. It is not compatible with wafers with bond pads or similar uncoated area requirements.
By using the 2-layer process disclosed in this application the prior art's limitations described above can now be overcome.